US3673289A - Quenching injection molded polycarbonate parts for fatigue resistance - Google Patents

Quenching injection molded polycarbonate parts for fatigue resistance Download PDF

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Publication number
US3673289A
US3673289A US6977A US3673289DA US3673289A US 3673289 A US3673289 A US 3673289A US 6977 A US6977 A US 6977A US 3673289D A US3673289D A US 3673289DA US 3673289 A US3673289 A US 3673289A
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Prior art keywords
parts
polycarbonate
mold
injection molded
temperature
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Expired - Lifetime
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US6977A
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John Gagliani
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International Business Machines Corp
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International Business Machines Corp
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/08—Heat treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B13/00—Conditioning or physical treatment of the material to be shaped
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/0001—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor characterised by the choice of material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/16—Cooling
    • B29C2035/1616—Cooling using liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • B29C2071/025—Quenching, i.e. rapid cooling of an object
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2069/00—Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2369/00—Characterised by the use of polycarbonates; Derivatives of polycarbonates

Definitions

  • ABSTRACT A process for the production of void free enhanced impact fatigue strength polycarbonate parts wherein parts are molded in a heated die and immediately after the molding cycle quenched in a liquid bath such as ice water.
  • This invention relates generally to polycarbonate plastics and more particularly to a method for making shaped polycarbonate articles having enhanced impact fatigue strength.
  • plastic for metal in many structural applications is desirable since significant savings can be realized by molding complex shapes rather than using multiple machining operations.
  • the plastic material must possess comparable physical characteristics. Moldable polycarbonate plastics have good temperature stability and good impact strength as required for structural members.
  • a structural member such as a machine part should possess excellent impact fatigue strength characteristics to assure that the part will possess a satisfactory service life in the environment for which it is designed.
  • the present invention utilizes the technique of molding polycarbonate parts in a mold which is maintained at an elevated temperature and immediately quenching the molded part in ice water upon removal from the mold cavity. Using an elevated mold temperature it is possible to eliminate vacuum voids in the formed part. The presence of voids is more prevalent at lower mold temperatures and in portions of a part having larger cross sectional dimensions.
  • Moldable polycarbonates sometimes identified as bisphenol-A polycarbonates commonly formed from reacting bisphenol-A with phosgene or with diphenyl carbonate find a rapidly growing field of application for molded parts. This material is more completely described in Polycarbonates" by William F. Christopher and Daniel W. Fox, Reinholt Publishing Corporation 1962. Comparative advantages are achieved by this material over other thermoplastic materials in such characteristics as: moldability to close tolerances and dimensional stability in use, good electrical resistance, heat resistance and self extinguishing characteristics, strength and modulus, high impact strength and toughness, and the ability to maintain properties over a wide temperature range.
  • Polycarbonate material can be molded successfully using mold temperatures as high as 350 F. Although it is impossible to use a room temperature mold it has been found more satisfactory to heat the mold to a temperature of 175 to 200 F. and in some applications better part quality is achieved by further increasing the mold temperature.
  • a part was molded having a 1.1 inch projection of square cross section with 0.376 inch dimensions projecting from an enlarged portion.
  • the enlarged portion was clamped in position and a repeated impact load of known magnitude applied to the cantilevered projection at a frequency of 1,800 cycles per minute until catastrophic fracture occurred.
  • the molding operation was accomplished using a mold thermostatically maintained at an elevated temperature, commonly in the range of 250 F., by circulating heated oil through heat exchange channels within the die set.
  • the mold Upon completion of the molding cycle, the mold is opened and the ejected part immediately immersed in a quenching bath of ice water at 0 to 5 C. wherein it remains until the entire cross section has been reduced in temperature.
  • the quenching may result in an increase in weight due to about 0.15 percent moisture absorption; however, this is dissipated within 48 hours and the part returns to the nonnal weight.
  • This quenching operation could also be accomplished using other liquids in the bath so long as such liquid is compatible with the part. Such liquid would not react with or dissolve the part.
  • EXAMPLE I An elongated part having a cross section of 0.376 inches square and a length of 1.1 inches extending from an enlarged section is formed within a mold maintained at 250 F.
  • the part is formed of bisphenol-A polycarbonate heated to a temperature of 570 F. and injected into the mold cavity using a 1,000 pound force. The part is allowed to remain in the mold for 90 seconds. Following opening of the mold, the part is removed and immediately quenched in ice water 0 to 3 C. for a period of 15 minutes, calculated to assure thorough cooling of the entire part cross section.
  • a method of forming moldable polycarbonate into an impact fatigue resistant part comprising:
  • said water bath is maintained at a temperature between 0 and 5 C.
  • polycarbonate material comprises a bisphenol-A polycarbonate resin conraining a filler of chopped glass fibers.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Polyesters Or Polycarbonates (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Abstract

A process for the production of void free enhanced impact fatigue strength polycarbonate parts wherein parts are molded in a heated die and immediately after the molding cycle quenched in a liquid bath such as ice water.

Description

nited States Patent Gagliani QUENCHING INJECTION MOLDED POLYCARBONATE PARTS FOR FATIGUE RESISTANCE John Gagliani, Rochester, Minn.
Inventor:
Assignee: International Business Machines Corporation, Armonk, N.Y.
Filed: Jan. 28, 1970 Appl. No.: 6,977
U.S. Cl ..264/28, 264/237, 264/348 lint. Cl. ..B29c 25/00 Field of Search ..264/237, 348, 178, 328, 346,
References Cited UNITED STATES PATENTS Loveless ..264/178 51 June 27, 1972 Raff et al.; Crystalline Olefin Polymers Part II; Interscience Pub. 1964; 'I'Pl 180.P65R3 pages 29- 32.
Christopher et al.; Polycarbonates Reinhold 1962; TP156P6C4 pages 93 & 94.
Primary Examiner-Julius Frome Assistant Examiner-Arthur l-l. Koeckert Y Attorney-Hanifin and J ancin and Robert w. Lahtinen [57] ABSTRACT A process for the production of void free enhanced impact fatigue strength polycarbonate parts wherein parts are molded in a heated die and immediately after the molding cycle quenched in a liquid bath such as ice water.
3 Claims, No Drawings QUENCHING INJECTION MOLDED POLYCARBONATE PARTS FOR FATIGUE RESISTANCE BACKGROUND OF THE INVENTION This invention relates generally to polycarbonate plastics and more particularly to a method for making shaped polycarbonate articles having enhanced impact fatigue strength.
The substitution of plastic for metal in many structural applications is desirable since significant savings can be realized by molding complex shapes rather than using multiple machining operations. To provide an adequate alternative; however, the plastic material must possess comparable physical characteristics. Moldable polycarbonate plastics have good temperature stability and good impact strength as required for structural members. In addition a structural member such as a machine part should possess excellent impact fatigue strength characteristics to assure that the part will possess a satisfactory service life in the environment for which it is designed.
The present invention utilizes the technique of molding polycarbonate parts in a mold which is maintained at an elevated temperature and immediately quenching the molded part in ice water upon removal from the mold cavity. Using an elevated mold temperature it is possible to eliminate vacuum voids in the formed part. The presence of voids is more prevalent at lower mold temperatures and in portions of a part having larger cross sectional dimensions.
When formed at the elevated temperature, the part immediately upon removal from the cavity is immersed in ice water, and quenched for a period calculated to reduce the temperature throughout the part. The impact fatigue characteristic of polycarbonate parts so processed was significantly enhanced and a like improvement, although of lesser magnitude, occurs in certain filled polycarbonate parts. When polycarbonate parts filled with 30% chopped glass fibers by weight were tested, the impact fatigue strength was found in all instances more than double.
It is an object of this invention to provide a process for molding polycarbonate parts having enhanced impact fatigue characteristics. It is a further object of the invention to provide a method for fabricating molded parts in which such enhanced impact fatigue characteristics are permanently imparted within the entire normal operating range of temperatures.
Moldable polycarbonates sometimes identified as bisphenol-A polycarbonates commonly formed from reacting bisphenol-A with phosgene or with diphenyl carbonate find a rapidly growing field of application for molded parts. This material is more completely described in Polycarbonates" by William F. Christopher and Daniel W. Fox, Reinholt Publishing Corporation 1962. Comparative advantages are achieved by this material over other thermoplastic materials in such characteristics as: moldability to close tolerances and dimensional stability in use, good electrical resistance, heat resistance and self extinguishing characteristics, strength and modulus, high impact strength and toughness, and the ability to maintain properties over a wide temperature range.
In studies of impact fatigue strength of these materials, it has been sought to improve the resistance to repeated impact loading and to extend the applicability to structural parts subjected to cyclic mechanical loading.
Polycarbonate material can be molded successfully using mold temperatures as high as 350 F. Although it is impossible to use a room temperature mold it has been found more satisfactory to heat the mold to a temperature of 175 to 200 F. and in some applications better part quality is achieved by further increasing the mold temperature.
In the present invention a part was molded having a 1.1 inch projection of square cross section with 0.376 inch dimensions projecting from an enlarged portion. In subsequent fatigue tests, the enlarged portion was clamped in position and a repeated impact load of known magnitude applied to the cantilevered projection at a frequency of 1,800 cycles per minute until catastrophic fracture occurred.
The molding operation was accomplished using a mold thermostatically maintained at an elevated temperature, commonly in the range of 250 F., by circulating heated oil through heat exchange channels within the die set. Upon completion of the molding cycle, the mold is opened and the ejected part immediately immersed in a quenching bath of ice water at 0 to 5 C. wherein it remains until the entire cross section has been reduced in temperature. The quenching may result in an increase in weight due to about 0.15 percent moisture absorption; however, this is dissipated within 48 hours and the part returns to the nonnal weight. This quenching operation could also be accomplished using other liquids in the bath so long as such liquid is compatible with the part. Such liquid would not react with or dissolve the part.
Subsequent impact fatigue tests indicate a substantial upgrading of the fatigue characteristic of quenched parts, which characteristic is permanently retained by the part even in operating temperature environments of F.
EXAMPLE I An elongated part having a cross section of 0.376 inches square and a length of 1.1 inches extending from an enlarged section is formed within a mold maintained at 250 F. The part is formed of bisphenol-A polycarbonate heated to a temperature of 570 F. and injected into the mold cavity using a 1,000 pound force. The part is allowed to remain in the mold for 90 seconds. Following opening of the mold, the part is removed and immediately quenched in ice water 0 to 3 C. for a period of 15 minutes, calculated to assure thorough cooling of the entire part cross section.
These parts are identified as quenched. One series of parts, identified as molded parts, were made by the same process with the exception of the quenching step. Following the mold cycle the parts were removed and placed in a compartmented corrugated container and allowed to cool to room temperature in accordance with the normal molding process. A]- ternate parts, identified as quenched parts, were quenched as described above.
The parts thus fabricated were tested for impact fatigue strength with results as indicated in the following table:
Fracture Force of Impact Number of Impacts Prior to in Lbs. Molded Parts Quenched Parts EXAMPLE ll Force of Impact Number of Impacts Prior to in Lbs. Molded Parts Quenched Parts What is claimed is:
l. A method of forming moldable polycarbonate into an impact fatigue resistant part comprising:
injecting polycarbonate material into a mold cavity which has been preheated to a temperature in excess of F., and
said water bath is maintained at a temperature between 0 and 5 C.
3. The method of claim 2 wherein the polycarbonate material comprises a bisphenol-A polycarbonate resin conraining a filler of chopped glass fibers.

Claims (2)

  1. 2. The method of claim 1 wherein the mold cavity into which the polycarbonate material is injected is preheated to and maintained at a predetermined temperature between 200* and 350* F., and said water bath is maintained at a temperature between 0* and 5* C.
  2. 3. The method of claim 2 wherein the polycarbonate material comprises a bisphenol-A polycarbonate resin containing a filler of chopped glass fibers.
US6977A 1970-01-28 1970-01-28 Quenching injection molded polycarbonate parts for fatigue resistance Expired - Lifetime US3673289A (en)

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US697770A 1970-01-28 1970-01-28

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US (1) US3673289A (en)
JP (1) JPS4911738B1 (en)
CA (1) CA953868A (en)
DE (1) DE2103313C3 (en)
FR (1) FR2075124A5 (en)
GB (1) GB1312902A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4068004A (en) * 1976-06-30 1978-01-10 Life Savers, Inc. System and method for cooling of gum base
US4246917A (en) * 1979-11-26 1981-01-27 Cafarelli Ralph J High-speed stabilization of molded parts
US4450133A (en) * 1979-11-26 1984-05-22 Cafarelli Ralph J Stabilization of molded parts
US4659533A (en) * 1985-09-16 1987-04-21 The Dow Chemical Company Process for the formation of large void-free thermoplastic articles
US20130227881A1 (en) * 2012-03-05 2013-09-05 Att Southern Inc. Recycled plastic composite composition
US20210372212A1 (en) * 2020-06-01 2021-12-02 Geodynamics, Inc. Quick connect setting kit and method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69516390T2 (en) * 1995-01-20 2000-12-07 General Electric Co., Schenectady Process for the tempering of thermoplastic objects

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3057013A (en) * 1960-02-15 1962-10-09 Du Pont Method for producing pipe
US3155756A (en) * 1960-03-08 1964-11-03 Bayer Ag Molding of stress-free polycarbonate articles
US3200182A (en) * 1961-01-07 1965-08-10 Bayer Ag Production of a stress-free polycarbonate shaped article
US3553303A (en) * 1967-12-21 1971-01-05 Phillips Petroleum Co Extruding thermoplastic tubing

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3057013A (en) * 1960-02-15 1962-10-09 Du Pont Method for producing pipe
US3155756A (en) * 1960-03-08 1964-11-03 Bayer Ag Molding of stress-free polycarbonate articles
US3200182A (en) * 1961-01-07 1965-08-10 Bayer Ag Production of a stress-free polycarbonate shaped article
US3553303A (en) * 1967-12-21 1971-01-05 Phillips Petroleum Co Extruding thermoplastic tubing

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Christopher et al.; Polycarbonates Reinhold 1962; TP156P6C4 pages 93 & 94. *
Raff et al.; Crystalline Olefin Polymers Part II; Interscience Pub. 1964; TP1180.P65R3 pages 29 32. *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4068004A (en) * 1976-06-30 1978-01-10 Life Savers, Inc. System and method for cooling of gum base
US4246917A (en) * 1979-11-26 1981-01-27 Cafarelli Ralph J High-speed stabilization of molded parts
US4450133A (en) * 1979-11-26 1984-05-22 Cafarelli Ralph J Stabilization of molded parts
US4659533A (en) * 1985-09-16 1987-04-21 The Dow Chemical Company Process for the formation of large void-free thermoplastic articles
US20130227881A1 (en) * 2012-03-05 2013-09-05 Att Southern Inc. Recycled plastic composite composition
US20130227880A1 (en) * 2012-03-05 2013-09-05 Att Southern, Inc. Recycled plastic composite composition
US9943997B2 (en) 2012-03-05 2018-04-17 Att Southern, Inc. Recycled plastic composite composition
US20210372212A1 (en) * 2020-06-01 2021-12-02 Geodynamics, Inc. Quick connect setting kit and method

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Publication number Publication date
GB1312902A (en) 1973-04-11
DE2103313B2 (en) 1980-04-30
JPS4911738B1 (en) 1974-03-19
FR2075124A5 (en) 1971-10-08
DE2103313C3 (en) 1980-12-18
DE2103313A1 (en) 1971-08-05
CA953868A (en) 1974-09-03

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